Bug#1101527: pandas fails its autopkgtests

[James Addison]

(hello - I feel some responsibility for this bug, because I have been
eager for matplotlib 3.10 to be included in trixie)

Although I haven't attempted to run the autopkgtests locally for this
version of pandas, I have begun inspecting the source package and
build logs.

Of the existing Debian patches, I felt that
versioned_importorskip.patch[1] seems potentially relevant -- it
describes that tests relying on specific, often database/client-server
libraries (e.g. mysql, postgresql) should be skipped when suitable
versions of Python libraries cannot be imported.

And another potential clue: the errors in the complete build log
mention fully-qualified Python error classnames (e.g.
pymysql.err.OperationalError) -- along with the file paths they are
imported from (e.g.
/usr/lib/python3/dist-packages/pymysql/connections.py).

...however, I didn't find any indication that the corresponding Debian
package(s) (python3-pymysql, continuing the example) were installed
during the build.

I _think_ that unittests3 is the test set to focus on (see the very
tail end of the buildlog).  I half-expected python3-pymsql to be
installed in the corresponding tests/control file -- but no, it is
commented-out[2].

On balance: I'm optimistic that the fix may be relatively
straightforward: figuring out why some Python packages are installed
on the build/test host when they shouldn't be.  But the tricky part
(if that theory is correct) is figuring out what has caused them to be
installed.

[1] - https://sources.debian.org/src/pandas/2.2.3%2Bdfsg-8/debian/patches/versioned_importorskip.patch/

[2] - https://sources.debian.org/src/pandas/2.2.3%2Bdfsg-8/debian/tests/control/#L37